Finishing mortar



United States Patent 3,498,809 FINISHING MORTAR Karl Olof Natanael Andersson, Skogsviksvagen 51, Danderyd, Sweden, and Stig Holmgren, Vasbygatan 3a, Sala, Sweden No Drawing. Filed Feb. 21, 1966, Ser. No. 528,836 Claims priority, application Sweden, Feb. 27, 1965, 2,599/65 Int. Cl. C04b 19/02 US. Cl. 106-115 14 Claims ABSTRACT OF THE DISCLOSURE This invention represents an improvement over the known finishing mortars (composed of a filler, a binder, and water) which involves utilizing as the binder a combination of (a) an inorganic gel which is the reaction product of an inorganic base and a metal salt and (b) a water soluble cellulose derivative.

It is known to produce a finishing or plastering mortar containing a Water-soluble cellulose derivative as a binder, inorganic filler material of different grain sizes, and water in an amount suflicient to impart to the mortar a suitable consistency. It is known also to such mortars to add, as an additional binder, slaked lime and mineral gelling substances, such as bentonite.

Certain finishing mortars of the kind here referred to are known as sand-putties. Such mortars are characteristic, interalia, by having a'binder content which is low as compared to that of conventional finishing mortars containing mainly lime, lime plus, cement, or gypsum as a binder, These sand-putties find use mainly for surface finishing 0n comparatively smooth concrete and light concrete walls. They are pre-fabricated to be ready for use and are stored up in a wet-mixed state. These finishing mortars have a putty-like character, their thick consistency being due, primarily, to the presence of the cellulose derivative This involves the drawback of necessitating the content of cellulose derivative or other Watersoluble thickener to be selected higher than would be required from a binding point of view alone. For this reason, said content usually is kept as high as from 0.5% to 1.0% which makes the finishing coat applied to the surface of a building more or less sensitive to water.

The present invention has for its object to highly improve the water resistance of finishing mortars, or sandputties, of the kind referred to. According to the invention, the Water-soluble cellulose derivative is substituted in par by a synthetic inorganic gel produced by reacting an inorganic base with a metal salt and adapted to take over the thickening function of the cellulose derivative. This modification also involves further advantages, the most important one being that of imparting to the finishing mortar a more pronounced thixotropic character which will improve the operating or applying characteristics. Thus the capacity of spray applicator equipment used has been found to increase by to 50% when spraying a product according to this invention, as compared to products hitherto used. Also, the mortar will exhibit excellent properties as regards its capability of filling out relatively deep cavities without shrinking-in and cracking.

The improved water resistance is due primarily to the reduced content of the water-soluble binder component. Such component, however, as a rule, cannot be omitted entirely, particularly in cases where the finishing mortar is to be used on smooth concrete surfaces or the like, a certain quantity of cellulose derivative or the like being then necessary in order to obtain satisfactory adhesion.

3,498,809 Patented Mar. 3, 1970 A certain amount of water-soluble cellulose derivative will also have the favourable effect of inhibiting separation of the finishing mortar during long-time storage.

The reduction in quantity of comparatively expensive cellulose derivatives will enable, within an unchanged frame of overall raw material cost, to add, in addition to the inorganic gel, a larger quantity of water resistant binders in the form of aqueous emulsions or dispersions which, on drying, will form water resistant films and, hence, will result in the obtainment of a practically water resistant product. As the said synthetic inorganic gel,

there is used, according to the invention, in the first place the reaction product obtained by reacting calcium hydroxide with aluminum sulphate. This reaction is suitably carried out by pouring a solution of aluminium sulphate into a slurry of slaked lime in water during vigorous stirring thereof. As an apparatus for effecting a sufficiently effective stirring, it is preferable to use a so-called dissolver or any other high-speed mixer equivalent thereto, although any other apparatus exerting the required mixing power may be employed.

Starting from a certain quantity of lime, the addition of aluminium sulphate may be varied depending on the desired gel viscosity and the desired excess of calcium hydroxide. Thus, by using equi-molecular quantities, it will also be possible to obtain a neutrally reacting gel. The viscosity of the gel, of course, will also depend on its water content. The mole ratio of base to the metal salt can range from about 31:1 to about 1:1, and preferably is from about 31:1 to about 7.8: 1.

The production of a mortar for finishing purposes may be exemplified as follows:

EXAMPLE A 200 kg. slaked lime is suspended in 250 kg. water, A solution of 30 kg. aluminium sulphate in 150 kg. water is added slowly while stirring vigourously, thereby forming a gel. Using this gel, a mortar of the following composition is produced:

kg. 6.6% cellulose ether solution 315 kg. gel

1150 kg. graded filler material, and water to sultable consistency.

Where an extra-high water resistance is desired, this mortar may have added to it between 25 and kg. of a water resistant binder, such as, for example, polyvinyl acetate, co-polymers of vinyl acetate, or acrylate, in the form of an emulsion or a dispersion.

In the above-mentioned example, the content of cellulose derivative before a possible extra addition of a water resistant binder is still as high as 0.4%. When adding water resistant binders in the form of dispersions or emulsions, however, this content may be substantially reduced. Thus, a very satisfactory finishing mortar having high water resistance has been produced with as little as 60 kg. of 6.6% cellulose ether solution and 105 kg. of a polyvinyl acetate dispersion, giving a content of no more than 0.2% water soluble binder. The amount of inorganic gel may also be varied. In the example, the gel quantity of the concentration stated amounts to 27% of the filler material quantity. Even gel additions of an order as low as 10% of the quantity of filler material will very favourably influence the properties of the finishing mortar from the points of view of workability and filling-in effect. A usable finishing mortar containing 40% gel by weight of the filler material has been produced.

EXAMPLE B Herebelow a Second procedure of producing a finishing mortar according to the invention will be described: 60 kg. of aluminium sulphate is dissolved in 435 kg.

3 i of water, after which 100 kg. of slaked lime is poured into the solution while stirring vigourously, thereby forming a gel. Added thereto are first 155 kg. of a 6.6% cellulose ether solution, and then 2150 kg. of a graded filler material while stirring, as well as water in a sufficient amount to obtain a suitable consistency.

The mortar thus obtained may, of course, have a water resistant binder added to it in proportions similar to those of Example A.

EXAMPLE C A third manner of producing a plastering mortar having a very good water resistance will now be described.

In a vessel, and using a dissolver, one mixes 480 kg. water, 240 kg. calcium hydrate and 400 kg. dolomite of a finely divided fraction, preferably having a grain size belw 0.25 mm. Added to this mixture, while continuing agitation with the dissolver, is a solution of 36 kg. aluminium sulphate in 180 kg. water, After stirring to a gelly consistency, the mixture thus obtained is pumped into a storage tank from which it is discharged for preparing the final product in a conventional concrete mixer as follows:

500 kg. pre-fabricated mixture of the kind just described 72 kg. 6% aqueous solution of a cellulose derivative 900 kg. dolomite, grain size 0 to 0.35 mm.

61 kg. water dispersion of a polyvinyl acetate co-polymer (having a good water resistance) Water to suitable consistency.

In this example a different mixing order has been followed, in that a portion of the graded filler material was added already in the preparatory mixture. This has been found to have a favourable influence on the consistency of the preparatory mixture.

As filler materials in the examples described, crushed and graded dolomite or limestone, respectively, with a maximum grain size of 0.5 mm. has been used. However, there is no objection to the use of granular materials of different compositions or of larger maximum grain sizes. Thus, it is possible to use filler materials of grain sizes as large as 1 mm., which may be desirable where particularly thick coats of plastering are to be applied. The filler material should, however, be graded as well as possible, i.e. it should follow generally accepted rules for the grading of filler material for plasters and mortars.

The product prepared in accordance with Example C has been found to possess, after setting, a resistance to mechanical wear in a wet state being 5 to times as as that of prior art products of the corresponding The use of a gel obtained from calcium hydroxide and aluminium sulphate as described hereinbefore has been found to involve a surprisingly satisfactory effect as regards capacity increase of the spraying equipment used for applying the product. It has been found by repeated tests that the capacity of such applicator equipment was increased by 25 to 50% in terms of litres per minute. The reason for this resides in the pronounced thixotropic properties of the product which enable the material to pass more readily through hoses and nozzles.

As already mentioned, a suitable inorganic gel may be produced by effecting reaction inwater between calcium hydroxide and aluminum sulphate. However, other inorganic bases and metal salts may be used, as well. In this case the only essential thing would be that the metallic element of the salt is capable of forming a hydroxide which is difiiculty soluble in water and is prone to forming gels, either in itself or by amphoteric reactions. The metal component thereof, besides aluminium, may be zinc, for example and in particular zinc and sulphate. To exemplify inorganic bases other than calcium hydroxide, ammonium hydroxide may be mentioned. In this latter case, the metal salt, without any inconvenience, may be a chloride, for example. As a measure of the usability of the gel, as a thickener in the finishing mortar,

the viscosity of the gel may be specified. Finishing mortars of excellent'qualities have been obtained when using a gel which, at a water content of about 65%, had a viscosity of between 100,000 and 200,000 cp., as measured at +20 C. with a Brookfield viscosimeter equipped with a so-called Helipath Stand. The gel of Example A has a viscosity of about 115,000 to 170,000 cp., measured as just described. The viscosity obtained of the gel will depend on the effectiveness of the mixing procedure.

What is to be claimed is:'

1. In the known method of producing a finishing mortar by admixing (a) a fine, granular, graded, inorganic filler material,

(b) a water soluble cellulose ether binder solution, and

(c) water in an amount to impart suitable consistency,

the improvement which comprises:

(1) bringing together calcium hydroxide and aluminum sulfate in a mole ratio from about 31:1 to 1:1 in a reaction zone under vigorous mixing conditions so as to form an inorganic gel (2) admixing said inorganic gel in the amount of 1040% based on the weight of the filler with said water soluble cellulose ether binder solution, said fine, granular, graded, inorganic filler material, and said water.

2. The method according to claim 1 which comprises additionally admixing a material to impart greater water resistance selected from the group consisting of polyvinyl acetate and the copolymers of vinyl acetate and acrylate in the form of emulsions and dispersions.

3. In the known method of producing a finishing mortar by admixing (a) a fine, granular, graded, inorganic filler material,

(b) a water soluble cellulose derivative binder, and

(c) water in an amount to impart suitable consistency,

the improvement which comprises:

(1) bringing an inorganic base selected from the group consisting of calcium hydroxide and ammonium hydroxide together in a reaction zone with a metal salt selected from the group consisting of aluminum sulfate, and zinc chloride in a mole ratio of base to salt from about 31:1 to 1:1 under vigorous mixing conditions so as to form an inorganic gel,

(2) admixing said inorganic gel in the amount of about 10-40% by weight based on the weight of the filler, with said water soluble cellulose derivative binder, said fine, granular, graded, inorganic filler material, and said water.

4. In the known combination of (a) a fine, granular, graded, inorganic filler material,

(b) a water soluble cellulose ether binder solution,

and

(c) water in an amount to impart a suitable consistency, which combination is useful as a finishing mortar and which has a putty-like character, the improvement in such mortar composition which comprises as part of the binder along with said cellulose ether binder solution, a synthetic inorganic gel which is the reaction product of calcium hydroxide and aluminum sulfate in a mole ratio of about 31:1 to 1:1, and with said gel being present in the amount of about 10-40% based on the weight of the filler, the improved mortar composition being characterized by ease of spray application, capability of filling out deep cavities without shrinking-in and cracking, and good water resistance.

5. A mortar composition in accordance with claim 4 which additionally contains a material to impart greater water resistance selected from the group consisting of polyvinyl acetate and the copolymers of vinyl acetate and acrylate in the form of emulsions and dispersions.

6. In the known combination of (a) a fine, granular, graded, inorganic filler material.

(b) a water soluble cellulose derivative binder, and

(c) water in an amount to impart a suitable consistency which combination is useful as a finishing mortar and which has a putty-like character, the improvement in such mortar composition which comprises as part of the binder along with said water soluble cellulose derivative binder about lO-40% by weight (based on the weight of the filler) of a synthetic inorganic gel which is the reaction product of an inorganic base selected from the group consisting of calcium hydroxide and ammonium hydroxide and a metal salt selected from the group consisting of aluminum sulfate, zinc sulfate and zinc chloride, wherein the mole ratio of said base to said salt is about 31:1 to 1:1, and the improved mortar composition being characterized by ease of spray application, capability of filling out deep cavities without shrinking-in and cracking, and good water resistance.

7. The method according to claim 1 which comprises bringing together said calcium hydroxide and said aluminum sulfate in a mole ratio of from about 31:1 to 7.8: 1.

8. The method according to claim 3 which comprises bringing calcium hydroxide together in a reaction zone with aluminum sulfate.

9. The mortar composition according to claim 4 wherein said calcium hydroxide and aluminum sulfate are in a mole ratio of about 3121 to 7.811,

10. The mortar composition according to claim 6 wherein said base and said salt are in a mole ratio of about 40:1 to 7.8:1.

11. The mortar composition according to claim 6 wherein said base is calcium hydroxide.

12. The mortar composition according to claim 6 wherein said salt is aluminum sulfate.

13. The mortar composition according to claim 6 wherein said salt is calcium hydroxide and said base is aluminum sulfate.

14. The mortar composition according to claim 6 wherein said Water soluble cellulose derivatives is a cellulose ether.

References Cited UNITED STATES PATENTS 2,592,345 4/ 1952 Schnell et al 106-115 FOREIGN PATENTS 696,965 9/ 1953 Great Britain.

JAMES E. POER, Primary Examiner US. Cl. X.R. 106-1l8, 119 

